This invention relates to an improved embodiment of a laser-beam instrumentation system described in U.S. Pat. No. 4,808,789 (now assigned to the applicant), in which it describes and claims generally semiconductor diode-pumped lasers, while the present invention includes both semiconductor-pumped and flashlamp-pumped (illuminated laser systems. It achieves the many applications of both types of the laser systems and performs rapid and low-cost instrumentations by means of a single laser unit that performs the work of numerous laser systems. The user can obtain long-wavelength, short-wavelength, fine-focus, broad-focus, ultraviolet, visible, or infrared laser beam from a single unit as desired. Ordinarily, these applications require separate laser systems which situation makes it very costly and requires particular space for keeping them. In contrast, this invention is a single unit which provides the characteristics of all these various laser systems in a single unit by merely interchanging the modules thereof.
The present invention has numerous other improvements over the preceding patented invention in that the entire system consists of a single instrumentation unit of numerous operations and applications. As stated, the system further includes the functions of more than a dozen conventional laser systems in a single unitary instrumentation system by interchanging the modules; that is, removing a module from one unit and inserting in into another unit to form a new type of laser-generating device in the infrared, visible, ultraviolet and even longer-wavelength x-ray radiation, depending on the module inserted into the system. Furthermore, the system particularly employs semiconductor diode lasers for the operative laser beam, or for optically pumping (illuminating) a solid-state laser rod selected from a group of laser rods characterized by ruby, neodymium-YAG, neodymium-glass, lithium-sapphire, alexandrite, and the like. In addition, the system console is adapted to accept any solid-state laser generator or any gas laser including helium-neon, and ion lasers such as argon laser, krypton laser, xenon laser, or molecular lasers such as a carbon dioxde laser or excimer laser. These laser systems readily can be inserted in the console or housing that includes the alternating-current rectifier and the control units for both the current and radiation producing sections such as those shown in FIG. 1.
The present invention further exhibits much improvement in efficiency of laser production over conventional laser systems, since it is generally provided with very efficient radiation emitters characterized by semiconduxtor giodes. The radiation emitted from the diodes is pure, stable, unadulterated with any impurities, as the general conventional-type lasers have the tendency to be occasionally bearing pollutant impurities. The present invention further greatly reduces the tendency of emitting heat from the laser generator as common laser systems do and need cooling by means of circulating air, water, or other fluid means, since heat reduces the laser emission efficiency. The service life of a flashlamp (of conventional laser systems) used for pumping the conventional laser systems is also short, typically 400 to 600 hours using the most efficient flashlamp, while diode-pump lifetime ranges more than 100,000 hours. These characteristics of the optical pumping lamp (flashlamp) make the conventional laser bulky and costly to produce, while the present diode-laser pumping system is small in size, compact, and relatively less costly to manufacture. Accordingly, the present solid-state laser production techniques are too wasteful in energy utilization, making the laser system very costly for employment in many technical applications.
The typical laser diodes that are employed in the present invention are: gallium arsenide (GaAs) which typically emits at 8000 angstroms, gallium-aluminum-arsenide (GaAIAs) which emits at 7500 to 9050 angstroms, indium-gallium-aesenic-phosphide (InGaAsP) emitting at 11,000 to 16,000 angstroms in the infrared, gallium-indium-aluminum-phosphide (GaInAlP) emitting at 6700 to 6800 angstroms, and their derivatives. There are still other diode lasers which are hybrids of these diode ingredients, and operate at various wavelengths depending on the power level applied for their emission. These diodes can be operated continuously or in pulsed modes, depending on the character of the circuit in which they are operating. Each of these modes has specific advantages and is selected for use in the different modules in the present laser system.
The diode laser further offers a conversion efficiency of 25 to 40 percent. This is to say that an input power of, for instance, 10 watts can produce 2.5 to 4 watts of laser radiation from the laser rod, because the radiation compatibility of the diode can be modulated to that of the laser rod by temperature-conditioning the diode. Additional advantages of a diode laser pump over the flashlamp is that the radiation from the diode laser can be very pure TEM.sub.oo, thus matching the operation mode of the laser rod. TEM.sub.oo operational mode is the fundamental performance format of a laser element and is derived from the phrase "Transverse Electromagnetic Mode", simulating a gaussian operational format, which is a most efficient performance mode of a laser system.
Furthermore, the thermal problems dominant in flashlamp-pumped systems are alleviated in diode-pumped laser systems, and inherent cooling operations are not difficult to achieve by the use of electrothermal (Peltier Effect) coolers, which are tiny in size and only require a small amount of current to operate, rather than water or air-cooling scheme necessary in conventional flashlamp-pumped process. Thermal birefringence effects and possible thermal focusing problems that reduce the laser-beam emission in the laser rod are also eliminated in diode-pumping mode. An important characteristic of the laser diode in its capability of being modulated easily at high speeds with high-amplitude stabilization that is imparted to the laser rod by the diode performance. An array of diodes operating in unison on a single microelectronic chip produce a cumulative radiant energy which can be focused with a focusing lens on the optical aperture (cross-sectional area) of an optical fiber for transmission of the laser beam. Thus, a very high energy from the diode array can be transferred through a fiberoptic cable to a remotely-located laser rod (as shown in one version of this invention). This type of laser embodiment can enhance the reduction in the size of the laserhead, as achieved in each of the modular embodiments shown in the drawings; furthermore, a small heatsink is provided in the laserhead to cool it when necessary. A heatsink is a highly thermoconductive material, such as a silver-coated thin sheet of nickel or copper. The system then can be made small, compact, and simple in construction. As will be seen from the drawings, the various modular styluses can be provided with thermal tuning, a harmonic generator (frequency amplifier), a Q-switch, and modelocking. Thus the design problems a-so are simplified and the system structure becomes simpler and less costly to manufacture.
The modular laser system generally employing the semiconductor diode laser for either optically pumping a solid-state laser rod or for furnishing the usable laser beam with nonlinear crystals (harmonic-wave generators) achieves a wide spectral output frequencies and power levels for a variety of applications, using any one of the different modular formats inherent to the present system. The output laser beam being principally diffraction-limited, TEM.sub.oo, and gaussian at all times. Because of the high efficiency of diode-laser performance, either as an optical pump source or as an emitter of pure laser radiation, and having the ability to be tuned by the temperature of the diode emitter, the system can generally achieve energy output rates of several orders of magnitude over the flashlamp-pumped conventional lasers. The resonant cavity thus can develop an extremely high-quality laser radiation. To add to these advantageous qualities, the system further can transmit therethrough a gaseous element for use in microelectronic processing, conventional industrial processing, in medical surgery and treatment, and military nonlethal applications.